Free jet with integrated oil separator

ABSTRACT

A centrifuge for cleaning the lubricating oil of an internal combustion engine, which simultaneously cleans the crankcase gases in which the separation result is improved by introducing crankcase gases (dashed arrows) directly, without any shielding baffles, into the oil mist generated by the drive nozzles in the centrifuge housing in order to produce a scrubbing effect, so that the crankcase gases are precleaned. For additional cleaning, guide vanes mounted on the rotor swirl the crankcase gas so that further residues are deposited along the walls of the housing, thereby making further measures to clean the crankcase gases unnecessary, with the result that the apparatus highly economical since it saves both material costs and maintenance costs.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a free jet centrifuge for the lubricating oil of an internal combustion engine with an integrated oil separator for crankcase gases of the internal combustion engine.

[0002] Free jet centrifuges of this general type are known in the art. For instance, the single figure of published German Patent application no. DE 43 11 906 A1 shows such a free jet centrifuge, which is driven by the lubricating oil to be centrifuged via reaction nozzles 34. The high speed of the centrifuge rotor is used to remove residues from the crankcase gas by means of slinger rings 70. The crankcase gas is withdrawn via a suction line 52.

[0003] The effect of this type of cleaning of the crankcase gases is limited, however. In view of the increasingly stringent governmental regulation of exhaust gases, cleaning by the proposed centrifuge is not sufficient, since the cleaned crankcase gases are supplied to the engine for combustion and thus affect the emission values in the exhaust. This is connected with the fact that the centrifuge inadequately separates the residues from the crankcase gas.

SUMMARY OF THE INVENTION

[0004] It is an object of the invention to provide an improved free jet centrifuge for cleaning both lubricating oil and crankcase gases of an internal combustion engine.

[0005] Another object of the invention is to provide a device for cleaning crankcase gases, which is formed by a free jet centrifuge for the lubricating oil of an internal combustion engine and which separates the residues from the crankcase gas with adequate efficiency.

[0006] These and other objects are achieved in accordance with the present invention by providing a free jet centrifuge for lubricating oil of an internal combustion engine, the centrifuge comprising a centrifuge rotor rotatable about an axis by jets of lubricating oil discharged from drive nozzles in the rotor, the rotor being configured as an oil separator for residues contained in crankcase gas of the engine; and a housing in which the rotor is rotatably supported, the housing comprising an oil inlet for supplying the rotor with the lubricating oil to be cleaned, an oil outlet for discharging clean lubricating oil, a crankcase gas supply line for supplying crankcase gases to be cleaned, and a suction line for withdrawing clean crankcase gases; wherein the crankcase gas supply line is connected to the housing in such a way that supplied crankcase gases are guided through a volume containing an oil mist produced by the drive nozzles of the rotor, and wherein the oil outlet and crankcase gas supply line are at least partially formed by a single connecting duct that opens into the housing of the free jet centrifuge.

[0007] The free jet centrifuge according to the invention includes a housing equipped, respectively, with an oil inlet and an oil outlet as well as a supply line and a suction line for the crankcase gas. The oil inlet is connected directly with the interior of the centrifuge rotor, so that the lubricating oil to be cleaned can be directly introduced there. The lubricating oil exits the rotor through the drive nozzles to reach the housing and is returned to the oil circuit through the oil outlet.

[0008] The crankcase gas supply line is connected with the crankcase in such a way that the crankcase gases can reach the housing of the oil centrifuge without increased flow loss. Due to the high rotational speed of the rotor, an entrained oil is removed from the crankcase gases as it sweeps past the rotor before it exits the housing in clean condition through the suction line.

[0009] According to the invention, however, still other separating effects are used when the crankcase gases are guided through the oil mist, which is produced by the centrifuge. In the oil mist, any residues contained in the crankcase gas are simultaneously separated. These are again primarily oil droplets, but can also be very finely distributed dirt particles that remain attached to the oil droplets of the oil mist. Thus, the crankcase gas reaches the centrifuge rotor in a pre-cleaned state, so that the separation efficiency for residues in the crankcase gas can be increased significantly. This ensures adequate oil separation from the crankcase gas by the centrifuge unit. Additional separation devices are not necessary. This eliminates, in particular, filter elements which require regular replacement. This provides an economically highly efficient solution since it eliminates on the one hand the production cost for these components and on the other hand the maintenance cost for replacing the oil separating elements.

[0010] It is particularly advantageous that the crankcase gas supply line for the crankcase gas and the oil outlet are formed at least in part by a single duct structure. This connecting duct ends in the housing of the free jet centrifuge. It is also possible for the oil outlet and the crankcase gas supply line to meet, so that they jointly form the connecting duct. This requires a sufficiently long common duct section so that a preliminary separation of the crankcase gases can occur. Another possibility is to have a single connecting duct leading from the crankcase housing directly to the centrifuge housing.

[0011] The connecting duct results in a simpler structure of the apparatus and thereby greater economic efficiency. The cross section of the connecting duct must be selected in such a way that the cleaned lubricating oil that runs from the centrifuge into the oil pan can freely flow away even if the amounts of blow-by gases are large. This achieves an additional scrubbing effect of the crankcase gases as they progress through the connecting duct in that the oil droplets in the crankcase gas are entrained by the return flow of cleaned lubricating oil. It is therefore particularly advantageous that the volume containing the oil mist, which is produced by the drive nozzles of the rotor, extends into the connecting duct. This expands the scrubbing effect to the largest possible flow path of the crankcase gas.

[0012] One specific embodiment of the centrifuge provides that the rotor be equipped with guide vanes along its outer circumference. These guide vanes serve to accelerate the crankcase gas in circumferential direction of the rotor. This improves the separation of residues in the crankcase gas in accordance with the mechanism of the centrifuge. Due to the centrifugal force, the residues are deposited along the housing wall and transported to the connecting duct of the housing. The crankcase gas drawn off through the suction line thus achieves a greater degree of purity.

[0013] A further measure to enhance the separation result is to mount at least one scrubber nozzle on the rotor in addition to the rotor drive nozzle(s). The main task of this scrubber nozzle is not to drive the rotor but to produce a scrubber jet that is advantageously directed radially away from the axis of rotation of the rotor. This scrubber jet results in additional cleaning of the crankcase gases, so that their quality can be further improved.

[0014] To make the centrifuge even more cost effective, the pressure relief valve provided for releasing the crankcase gases can be integrated into the housing structure. This saves primarily production and material costs. Consequently, this measure leads to a greater economic efficiency of the separator of the invention.

[0015] These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or the drawings, and the individual features each may be implemented in embodiments of the invention either alone or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawings in which:

[0017]FIG. 1 is a schematic illustration of the arrangement of a combined lubricating oil centrifuge with crankcase gas separation, and

[0018]FIG. 2 is a cross section through the center of a centrifuge according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0019]FIG. 1 shows a schematic diagram of an internal combustion engine 10 and a centrifuge 11 for cleaning the lubricating oil of the internal combustion engine. The centrifuge has a housing 12 and a rotor 13 that is rotatably supported in the housing. The centrifuge is rotated by a drive nozzle 14. It is supplied with lubricating oil to be cleaned from an oil circuit 15. The oil circuit is schematically reduced to a pump 16 and a lubrication point 17. The oil circuit further comprises an oil pan 18 of the internal combustion engine. The centrifuge is arranged in a bypass flow relative to the oil circuit 15. Oil is supplied to the centrifuge via an oil inlet 20. The cleaned lubricating oil, after exiting from the drive nozzle 14, is returned to the oil pan from the housing via an oil outlet 19.

[0020] Also provided on the housing is a crankcase gas supply line 21 through which the crankcase gases from the internal combustion engine can be conducted into the housing 12 of the centrifuge. The inlet point is located in an area that forms a volume 22 in the housing for the oil mist produced by the drive nozzle 14. The nozzle requires this expansion volume in order to rotate the rotor. Crankcase gas supply line 21 and oil outlet 19 open out into a common connecting duct 27, which consequently has flow in both directions and must therefore have a correspondingly large cross section.

[0021] Through volume 22, the crankcase gas reaches the rotor, which it must pass along the wall of the housing to reach a suction line 23 in the part of the housing that is located opposite volume 22. The crankcase gases are made to swirl around the rotor by guide vanes 24. As a result, any particles and oil droplets contained in the crankcase gas are deposited by centrifugal force along the wall of housing 12. The clean crankcase gas exits the housing 12 through the suction line 23 and passes a pressure relief valve 25. If the valve is open, the crankcase gas is sucked into the air intake tract 26 of the internal combustion engine.

[0022]FIG. 2 shows a detailed configuration of the centrifuge. Here, instead of an oil outlet and a crankcase gas supply line, a common connecting duct 27 is provided on housing 12. The housing is sealed relative to the mounting location by means of gaskets. The mounting location can be on the internal combustion engine itself. Under these conditions, the paths for supplying the crankcase gases and the lubricating oil are particularly short.

[0023] Thus, the housing comprises a housing base 28, which is mounted to the internal combustion engine (FIG. 1) by a molded seal 29. Furthermore, a screw-type bell 30, in which a pressure relief valve 25 is accommodated as an integral component, is provided as the cover of the centrifuge housing. The pressure relief valve comprises a membrane 33, which is biased to an open position by a spring 32, but is drawn against a valve seat 34 to seal the valve if the negative pressure in the air intake (FIG. 1) of the internal combustion engine becomes too high.

[0024] The rotor 13 may be made of synthetic resin material and advantageously comprises two shells 35 that are welded together. It is rotatably supported in housing 12 in a ball bearing 36 and a sleeve bearing 37. The sleeve bearing 37 simultaneously forms an inlet 38 in the rotor for the lubricating oil. The supply of lubricating oil can be controlled by an intake valve 39.

[0025] The lubricating oil circuit in the centrifuge is indicated by solid arrows; the flow of crankcase gas by dashed arrows. The lubricating oil reaches a central pipe 40 of the rotor through the intake valve 39 and the inlet 38 and from there passes through openings 41 into a separating volume 42 of the rotor. As the dirt particles are being deposited along the outer walls of the rotor, the oil stream exits the rotor through the drive nozzle 14 and a scrubber nozzle 43. The scrubber nozzle 43 produces a jet that is directed radially away from the rotor and causes any entrained residues to be flushed out of the crankcase gas. The crankcase gas in volume 22 is indicated by dots. From this volume, the lubricating oil, which collects on a housing floor 44, exits the housing through the connecting duct 27.

[0026] The crankcase gas flows against the return flow of the lubricating oil. After leaving the connecting duct 27, the crankcase gas is guided directly into volume 22. There are no barriers or baffles at all that would prevent the crankcase gas from mixing with the oil mist. This causes any residues to be effectively flushed out of the crankcase gas. Subsequently, the crankcase gas is directed along the guide vanes 24 to the upper part of the housing and from there into the pressure relief valve 25. At this point, the crankcase gas is largely free from residues so that it can be readily burned in the internal combustion engine.

[0027] The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations falling within the scope of the appended claims and equivalents thereof. 

What is claimed is:
 1. A free jet centrifuge for lubricating oil of an internal combustion engine, said centrifuge comprising: a centrifuge rotor rotatable about an axis by jets of oil discharged from drive nozzles in said rotor, said rotor being configured as an oil separator for residues contained in crankcase gas of the engine; and a housing in which the rotor is rotatably supported, said housing comprising an oil inlet for supplying the rotor with the lubricating oil to be cleaned, an oil outlet for discharging clean lubricating oil, a crankcase gas supply line for supplying crankcase gases to be cleaned, and a suction line for withdrawing clean crankcase gases; wherein the crankcase gas supply line is connected to the housing in such a way that supplied crankcase gases are guided through a volume containing an oil mist produced by drive nozzles of the rotor, and wherein the oil outlet and crankcase gas supply line are at least partially formed by a single connecting duct that opens into the housing of the free jet centrifuge.
 2. A free jet centrifuge according to claim 2, wherein the volume containing the oil mist extends into the connecting duct.
 3. A free jet centrifuge according to claim 1, wherein the rotor is equipped with guide vanes for accelerating the crankcase gas in circumferential direction of the rotor.
 4. A free jet centrifuge according to claim 3, wherein said guide vanes are disposed along the outer circumference the rotor.
 5. A free jet centrifuge according to claim 1, wherein the rotor further comprises at least one additional scrubber nozzle to enhance cleaning of the crankcase gases.
 6. A free jet centrifuge according to claim 5, wherein said scrubber nozzle discharges a scrubber jet in a radially outward direction relative to the axis of rotation of the rotor.
 7. A free jet centrifuge according to claim 1, further comprising a pressure relief valve for the crankcase gas, wherein said pressure relief valve is integrated into the centrifuge housing. 